I have a few animation mods installed in single player which allow me to apply certain poses or animations to guarding thralls in my base but they constantly revert back to combat stance. Does anybody know how to permanently apply a certain pose to them?
Hi and welcome to the forums 
Have you tried Emotes for Thralls (see link below)? It doesn’t offer every emote possible, but it does create tokens that sit in a thralls inventory and make them stick to an emote. (After a reset/when they render in, they might start off in a default emote/non-emote, but they’ll always go back tot he emote set.)
(Also worth noting, some of the emotes - crafted in Social Thralls Jug - are for followers and some are for ‘worker’ thralls (bench thralls) - the ones for workers act as mini ‘workstations’ that get placed,the are hidden by the thrall’s body when placed in the station - can be hard to find again later if you don’t take note of where the ‘pebble’ bit was to start with. Placing a worker token in a follower’s inventory won’t do anything/stops them emoting.)
I hope it helps